Buggy code:
public abstract class Connection implements java . sql . Connection , ConnectionCallbackInterface { public Agent agent_ ; public DatabaseMetaData databaseMetaData_ ; final WeakHashMap openStatements_ = new WeakHashMap ( ) ; final WeakHashMap CommitAndRollbackListeners_ = new WeakHashMap ( ) ; private SqlWarning warnings_ = null ; public transient String user_ ; public boolean retrieveMessageText_ ; protected boolean jdbcReadOnly_ ; private int holdability = JDBC30Translation . HOLD_CURSORS_OVER_COMMIT ; public String databaseName_ ; public String productID_ ; protected EncryptionManager encryptionManager_ ; private Statement setTransactionIsolationStmt = null ; protected boolean open_ = true ; protected boolean availableForReuse_ = false ; public int isolation_ = Configuration . defaultIsolation ; public boolean autoCommit_ = true ; protected boolean inUnitOfWork_ = false ; private boolean accumulated440ForMessageProcFailure_ = false ; private boolean accumulated444ForMessageProcFailure_ = false ; private boolean accumulatedSetReadOnlyWarning_ = false ; protected boolean isXAConnection_ = false ; public static final int XA_T0_NOT_ASSOCIATED = 0 ; public static final int XA_T1_ASSOCIATED = 1 ; private int xaState_ = Connection . XA_T0_NOT_ASSOCIATED ; public int xaHostVersion_ = 0 ; public int loginTimeout_ ; public ClientDataSource dataSource_ ; public String serverNameIP_ ; public int portNumber_ ; public Hashtable clientCursorNameCache_ = new Hashtable ( ) ; public boolean canUseCachedConnectBytes_ = false ; public int commBufferSize_ = 32767 ; public boolean resetConnectionAtFirstSql_ = false ; protected Connection ( org . apache . derby . client . am . LogWriter logWriter , String user , String password , ClientDataSource dataSource ) throws SqlException { } protected Connection ( org . apache . derby . client . am . LogWriter logWriter , String user , String password , boolean isXAConn , ClientDataSource dataSource ) throws SqlException { } protected void initConnection ( org . apache . derby . client . am . LogWriter logWriter , String user , ClientDataSource dataSource ) throws SqlException { } protected Connection ( org . apache . derby . client . am . LogWriter logWriter , boolean isXAConn , ClientDataSource dataSource ) throws SqlException { } protected void resetConnection ( LogWriter logWriter , String user , ClientDataSource ds , boolean recomputeFromDataSource ) throws SqlException { } protected void resetConnection ( LogWriter logWriter , String databaseName , Properties properties ) throws SqlException { } protected Connection ( LogWriter logWriter , int driverManagerLoginTimeout , String serverName , int portNumber , String databaseName , Properties properties ) throws SqlException { } protected void finalize ( ) throws Throwable { } public synchronized java . sql . Statement createStatement ( ) throws SQLException { } public synchronized PreparedStatement prepareStatement ( String sql ) throws SQLException { } public synchronized PreparedStatement preparePositionedUpdateStatement ( String sql , Section querySection ) throws SqlException { } public synchronized CallableStatement prepareCall ( String sql ) throws SQLException { } synchronized PreparedStatement prepareDynamicCatalogQuery ( String sql ) throws SqlException { } public String nativeSQL ( String sql ) throws SQLException { } public synchronized String nativeSQLX ( String sql ) throws SqlException { } protected abstract boolean allowLocalCommitRollback_ ( ) throws SqlException { } public synchronized void setAutoCommit ( boolean autoCommit ) throws SQLException { } public boolean getAutoCommit ( ) throws SQLException { } public synchronized void commit ( ) throws SQLException { } private void checkForInvalidXAStateOnCommitOrRollback ( ) throws SqlException { } public void flowCommit ( ) throws SqlException { } public boolean flowAutoCommit ( ) throws SqlException { } public boolean willAutoCommitGenerateFlow ( ) throws SqlException { } void writeAutoCommit ( ) throws SqlException { } public void writeCommit ( ) throws SqlException { } void readAutoCommit ( ) throws SqlException { } public void readCommit ( ) throws SqlException { } public synchronized void rollback ( ) throws SQLException { } protected void flowRollback ( ) throws SqlException { } public void writeRollback ( ) throws SqlException { } public void readRollback ( ) throws SqlException { } public synchronized void close ( ) throws SQLException { } void checkForTransactionInProgress ( ) throws SqlException { if ( ( ( ! ( autoCommit_ ) ) && ( inUnitOfWork_ ) ) && ( ! ( allowCloseInUOW_ ( ) ) ) ) { <START_BUG> throw new SqlException ( agent_ . logWriter_ , new MessageId ( SQLState . CANNOT_CLOSE_ACTIVE_XA_CONNECTION ) ) ; <END_BUG> } } public synchronized void closeX ( ) throws SQLException { } public synchronized void closeResources ( ) throws SQLException { } private void closeResourcesX ( ) throws SQLException { } protected abstract boolean isGlobalPending_ ( ) { } public synchronized void closeForReuse ( ) throws SqlException { } private void flowClose ( ) throws SqlException { } protected abstract void markClosed_ ( ) { } public void markClosed ( ) { } private void markClosedForReuse ( ) { } private void markStatementsClosed ( ) { } private void writeCloseStatements ( ) throws SqlException { } private void readCloseStatements ( ) throws SqlException { } public boolean isPhysicalConnClosed ( ) { } public boolean isClosed ( ) { } public boolean isClosedX ( ) { } private static String DERBY_TRANSACTION_REPEATABLE_READ = "RS" ; private static String DERBY_TRANSACTION_SERIALIZABLE = "RR" ; private static String DERBY_TRANSACTION_READ_COMMITTED = "CS" ; private static String DERBY_TRANSACTION_READ_UNCOMMITTED = "UR" ; public synchronized void setTransactionIsolation ( int level ) throws SQLException { } public int getTransactionIsolation ( ) throws SQLException { } public SQLWarning getWarnings ( ) { } public synchronized void clearWarnings ( ) throws SQLException { } public void clearWarningsX ( ) throws SqlException { } public java . sql . DatabaseMetaData getMetaData ( ) throws SQLException { } public synchronized void setReadOnly ( boolean readOnly ) throws SQLException { } public boolean isReadOnly ( ) throws SQLException { } public synchronized void setCatalog ( String catalog ) throws SQLException { } public String getCatalog ( ) throws SQLException { } public synchronized java . sql . Statement createStatement ( int resultSetType , int resultSetConcurrency ) throws SQLException { } public synchronized PreparedStatement prepareStatement ( String sql , int resultSetType , int resultSetConcurrency ) throws SQLException { }

Fix:
throw new SqlException ( agent_ . logWriter_ , new MessageId ( SQLState . CANNOT_CLOSE_ACTIVE_CONNECTION ) ) ;